Back light module of liquid crystal display device

ABSTRACT

The back light module of LCD device of the present invention is to use the two ends of reflecting plate to roll up and cover light generating units and reaching the function of lamp reflector. Also, the problem of EMI (electric magnetic interference) can be overcome by covering a shell with an EMI protection function on the roll up ends and/or coating or covering the metal with an EMI protection function on one surface of the reflecting plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a back light module of LCD device, and moreparticularly to a back light module of LCD device using a reflectingplate as a lamp reflector to reflect the light generated by lightreflecting generating units and using a metallic material installed on asurface of the reflecting plate and/or a coupling elements to overcomethe EMI problem.

2. Description of the Prior Art

A traditional back light module of an LCD (liquid crystal display)device generally comprises a support frame, a light guiding plate, alamp module, a reflecting plate assembled under the bottom of lightguiding plate, and various optical films assembled on the upper of thelight guiding plate. The various optical films include a diffusing film,a light condensing film, a light enhancement film, a prism film, and soon. The lamp module includes a U-shaped lamp reflector reflecting thelight emitted from the lamp into the light guiding plate. Furthermore,the light guiding plate guides the light to the front LCD device.

In the conventional back light module, the lamp is assembled within theU-shaped lamp reflector. Nevertheless, there are commonly matchingproblems occurred among the U-shaped lamp reflector, the light guidingplate, and the reflecting plate, in practice. These matching problemsalways cause defective phenomenons of dark region, light leakage, darkstripe, and wrinkling in some areas of the back light module. Moreover,the U-shaped lamp reflector is generally made of metallic materials andis harder than the light guiding plate, so the light guiding plate isscraped easily to generate dust during assembly or re-module processes.

In the conventional arts, the lamp module of the back light module issupported by a plastic frame (i.e., support frame) which is fixed byscrews in back light module assembly process. However, the plastic framewill deform and oppress the lamp when the assembling screws are turnedto tighten them. This causes the lamp bent and dark regions, so thedisplaying quality will reduce.

Furthermore, the lamp reflector of the lamp module and the reflectingplate compress each other easily, so the wrinkling phenomenon will occurin the reflecting plate.

Besides, the lamp reflector, the light guiding plate, and the reflectingplate are tightly connected with each other. While the LCD devicecomposed of the back light module and the LCD panel processes with shocktest, the lamp reflector compresses the light guiding plate and thereflecting plate, and so the drop test is failure. Namely, the structurementioned above results in that toleration for collision or droppinggoes down. Therefore, the displaying quality is reduced, and even theLCD penal can not further use due to some external forces under generalcollisions.

Hence, people familiar with those skills in the art tried to fabricate aback light module without the lamp reflector for LCD device. Forexample, U.S. Patent No. U.S. 2003/0043314A1 discloses a back lightmodule without U-shaped lamp reflector. However, the back light modulementioned above uses circle-shaped lamp, not linear-shaped lightgenerating unit. Moreover, the back light module uses a reflecting plateto cover the lamp for replacing the lamp reflector in the conventionalarts. However, the conventional lamp reflector is metal to avoidelectromagnetic interference (EMI) problem for eliminating interferencein image quality. Accordingly, the LCD device without lamp reflectorcauses electromagnetic interference (EMI) problem. Furthermore, thewrinkle of the reflecting plate resulted from temperature variabilitystill exits in the patent.

Besides, U.S. Patent Application No. 2002/0021383A1 discloses astructure of back light module. A reflecting plate is banded upward toform an upper plate for avoiding the problems of light leakage andwrinkle. Similarly, this patent application still does not useconventional metal lamp reflector and has the electromagneticinterference.

In accordance with problems mentioned above, the inventor haveresearched extensively in the back light module of LCD device and thencompleted the present invention.

SUMMARY OF THE INVENTION

The present invention provides a back light module of LCD device. Theback light module comprises a support frame, at least one lightgenerating unit, a light reflecting plate, and a light guiding plate.The support frame has lamp and support elements thereon. The lightgenerating unit has coupling elements to engage with the supportelements respectively installed on two ends thereof. The lightreflecting plate is installed on the support frame for reflecting alight generated by the light generating unit upwards, and two ends ofthe reflecting plate are bent upward. The light guiding plate isinstalled on the reflecting plate for guiding light. In such case, ametallic material for isolating electromagnetic interference isinstalled on a surface of the reflecting plate, a surface of thecoupling elements, or the combination thereof.

The present invention also provides a back light module of LCD deviceusing a different assembling design. The back light module comprises asupport frame, a light reflecting plate, a light guiding plate, and atleast one light generating unit. The light reflecting plate is installedon the support frame and two ends of the reflecting plate are bentupward. The light guiding plate is installed on the reflecting plate,two side of the light guiding plate respectively have an indentation,and support elements are formed in the indentations. The lightgenerating unit is installed in corresponding indentation and has twocoupling elements to engage with the support elements respectivelyinstalled on two ends of the light generating unit. A light generated bythe light generating unit is reflected upwards, and is guided by thelight guiding plate. In such case, a metallic material for isolatingelectromagnetic interference is installed on a surface of the reflectingplate, a surface of the coupling elements, or the combination thereof.

The present invention further provides a back light module of LCD deviceusing another different assembling design. The back light modulecomprises a support frame, at least one light generating unit, a lightreflecting plate, and a light guiding plate. The light generating unithas two coupling elements respectively installed on two ends thereof.The light reflecting plate is installed between the light generatingunit and the support frame for reflecting a light generated by the lightgenerating unit upwards. Two ends of the reflecting plate are bentupward. The light guiding plate is installed on the reflecting plate forguiding light. In such case, a metallic material for isolatingelectromagnetic interference is installed on a surface of the reflectingplate, a surface of the coupling elements, or the combination thereof.

The back light modules according to the present invention can avoid thepossibility of assembly interference among the lamp, the lightreflecting plate, and the light guiding, and overcome the problems oflight leakage, dark stripe, wrinkling, and EMI.

The back light modules according to the present invention employ thelight reflecting plate with two ends bended upward to cover the lightgenerating unit for replacing the lamp reflector in the conventionalarts. Furthermore, the EMI problem can be overcame by coating orcovering the metallic material on the surface of the reflecting surfaceand/or the coupling elements.

Besides, the reflecting plate can be divided into two portions to coverthe light generating unit. For example, the light generating unit iscovered by an L-shaped upper cover and a bottom reflecting plate of thereflecting plate to reduce the influence for the light guiding plate,the light reflecting plate, resulted from the heating of the lightgenerating unit. The L-shaped upper cover and the bottom reflectingplate can be fixed by the support elements and the covering elementsusing as tongue-and-groove joint. Moreover, the bottom reflecting platecan be bent upward to overlap the L-shaped upper cover for eliminatinglight leakage. The wrinkling problem of the reflecting plate due to theenvironment temperature variability resulted from the light generatingplate heating can be reduced by this design.

In another embodiment of the back light module of LCD device accordingto the present invention, the light generating unit is installed on oneend or two ends of the light guiding plate. The end(s) on that the lightgenerating unit is (are) installed extends outward to form supportelements for supporting the light generating unit. The reflecting platebelow the light guiding plate is bent upwards to cover the lightgenerating unit, and the reflecting plate can function as lampreflector.

Accordingly, the back light module of the present invention does notneed the conventional lamp reflector, so the winkling problem due toassembly of the lamp module can be avoided. Moreover, the assembly issimpler and the production cost is reduced because the light generatingunit is installed on the support frame or the light guiding plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an embodiment of a back lightmodule of LCD device in the present invention;

FIG. 2 illustrates a schematic diagram of another embodiment of a backlight module of LCD device in the present invention;

FIG. 3 illustrates a schematic diagram of a further embodiment of a backlight module of LCD device in the present invention;

FIG. 4 illustrates a partial schematic diagram of the engaging actionfor the coupling elements of the light generating unit and the supportelements of the support frame in FIG. 1;

FIG. 5 illustrates a partial schematic diagram of the engaging actionfor the coupling elements of the light generating unit and the supportelements of the light guiding plate in FIG. 2;

FIG. 6 illustrates a partial schematic diagram of the engaging actionfor the coupling elements of the light generating unit and the supportelements of the support stand in FIG. 3;

FIG. 7 illustrates a cross-sectional view of the back light module inFIG. 1; and

FIG. 8 illustrates a cross-sectional view of the back light module inFIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention has been illustrated by reference to the preferredembodiments. However, the embodiments are only used to illustrate thepresent invention and are not to limit the scope of the presentinvention.

FIG. 1 is a schematic diagram of an embodiment of a back light module ofLCD device according to the present invention, and illustrates thecorresponding relationship before assembling among the devices in theback light module. The back light module comprises a support frame 1, areflecting plate 2, a light guiding plate 3, light generating units 4,and one or many optical films 5. The reflecting plate 2 reflects a lightgenerated by the light generating units 4 to the light guiding plate 3.The light guiding plate 3 guides the light to the LCD panel (not shown).The light generating units 4 is installed on one or two sides of thesupport frame 1, and the support elements 11 are formed on the two endsof the support frame 1. In order to clearly express the position of thesupport elements 11 on the support frame 1, in FIG. 4, one corner of thesupport frame 1 is cut out to expose the support elements 11. Inpractice, however, the corner of the support frame 1 has not been cutout. Moreover, coupling elements 41 can be hollowed cylinders to sheathethe ends of the light generating unit 4 therein. In FIG. 1, the left endof the light generating unit 4 placed in the coupling elements 41 aredraw with dotted line to represent for clearly understanding thecomponent relationship between the coupling elements 41 and lightgenerating unit 4. Coupling elements 41 are installed on the two ends ofthe light generating unit 4 respectively to make the light generatingunit 4 and the support elements 11 engage with each other. Moreover, thecoupling elements 41 have a conductive wire 44 to electrically connectwith power supply. The two sides of the reflecting plate 2, incorrespondent with the position of the light generating unit 4, extendan estimated length, and the extend portions are rolled upward to coverthe light generating unit 4 as lamp reflector. The reflecting plate 2can be fixed on the support frame 1 and on the light guiding plate 3 byadhesive (e.g., twin adhesive) or tongue-and-groove joint. In FIG. 1,the right side of the reflecting plate 2 displays a shape of finishedreflecting plate 2, the left side displays a shape of unfinished thereflecting plate 2, and the dotted line at the right side represents thecurved shape of the reflecting plate 2 for easily understanding theembodiment.

In the embodiment, the electromagnetic interference (EMI) can beeliminated by coating, covering, or pasting with a metallic material(not shown) on the surface(s) of the coupling elements 41 or any onesurface of reflecting plate 2. It is preferred to coat, cover, or pasteon the bottom surface of the reflecting plate 2 (i.e., the oppositesurface to the light guiding plate 3). Therefore, the present inventioncan eliminate EMI problems. In such case, the metallic material can beany metal capable of isolating EMI, such as Cu, Ni, Al, or thecombination thereof. Moreover, the quantity of the light generating unitcan be one or many, depending on the desired purpose. In general, thereare two light generating units and the two light generating units arerespectively on the two sides of the back light module.

FIG. 4 illustrates a partial schematic diagram of the engaging actionfor the coupling elements 41 of the light generating unit 4 and thesupport elements 11 of the support frame 1 in FIG. 1.

FIG. 7 illustrates a cross-sectional view along a cross-section lineconnecting with the left and right support elements 11 of the back lightmodule in FIG. 1. However, there are quite many elements in FIG. 1, andthe cross-section line is not drawn to succinctly describe the figurefor avoiding perplexing to understand the present invention.

In the embodiment, the extending portions of the reflecting plate arecurved upwards and covered the light generating unit as lamp reflector.As mentioned above, the reflecting plate can be divided into twoportions (e.g., an upper cover and a bottom reflecting plate) to coverthe light generating units for reducing the heat influence of the lightgenerating units on other devices, such as the reflecting plate. Forexample, the reflecting plate can be composed of L-shaped upper coversand a bottom reflecting plate. The L-shaped upper covers and the bottomreflecting plate can be fixed by tongue-and-groove joint. Furthermore,the two sides of the bottom reflecting plate can be slightly curvedupwards to overlap the L-shaped upper covers for eliminating the problemof light leakage. The wrinkling problem of the reflecting plate due tothe surrounding temperature variability resulted from the lightgenerating plate can be reduced through this design.

Please refer to FIG. 2. FIG. 2 illustrates a schematic diagram ofanother embodiment of a back light module of LCD device in the presentinvention. The back light module of LCD device comprises a support frame1, a reflecting plate 2, a light guiding plate 3, light generating units4, and one or many optical films 5. The reflecting plate 2 reflects alight generated by the light generating units 4 to the light guidingplate 3. The light guiding plate 3 guides the light to the LCD panel.Two indentations are formed on the two sides of the light guiding plate3 respectively, and the two ends of the indentations have supportelements 31 to support the light generating unit 4. Similarly, couplingelements 41 are installed on the two ends of light generating unit 4respectively, and support elements 31 on the light guiding plate 3 andthe coupling elements 41 engage. Moreover, the coupling elements 41respectively have a conductive wire 44 to electrically connect withpower supply. The two sides of the reflecting plate 2 extend anestimated length, and the extend portions are rolled upward to cover thelight generating unit 4 as lamp reflector. Similarly, for easilyunderstanding the embodiment, the right side of the reflecting plate 2displays a shape of finished reflecting plate 2, and the left sidedisplays a shape of un-finished the reflecting plate 2.

In the embodiment, the electromagnetic interference (EMI) can beeliminated by coating, covering, or pasting with a metallic material(not shown) of isolating EMI on the surface of the coupling element 41or any one surface of reflecting plate 2. Therefore, the presentinvention can eliminate EMI problems. In such case, the metallicmaterial can be any metal capable of isolating EMI, such as Cu, Ni, Al,or the combination thereof. Moreover, the quantity of the lightgenerating unit can be two or many. Furthermore, indentations are notonly formed on the two sides of the light guiding plate, but also onother locations of the light guiding plate for installing lightgenerating units therein. In general, there are two light generatingunits respectively on the indentations at the two sides of the lightguiding plate respectively.

FIG. 5 illustrates a partial schematic diagram of the engaging actionfor the coupling elements 41 of the light generating unit 4 and thesupport elements 31 of the light guiding plate 3 in FIG. 2.

FIG. 8 illustrates a cross-sectional view along a cross-section lineconnecting with the left and right support elements 31 of the back lightmodule in FIG. 2.

In the embodiment, the extending portions of the reflecting plate arecurved upwards and covered the light generating unit as lamp reflector.As mentioned above, the reflecting plate can be divided into an L-shapedupper cover and a bottom reflecting plate to cover the light generatingunits for reducing the heat influence of the light generating units. Thetwo sides of the bottom reflecting plate can be slightly curved upwardsto overlap the L-shaped upper covers for eliminating the problem oflight leakage. Moreover, the wrinkling problem of the reflecting platedue to the surrounding temperature variability resulted from the lightgenerating plate can be reduced through this design.

Please refer to FIG. 3. FIG. 3 illustrates a schematic diagram of afurther embodiment of a back light module of LCD device in the presentinvention. The back light module also comprises a support frame 1, areflecting plate 2, a light guiding plate 3, light generating units 4,and one or many optical films 5. The support frame 1 supports otherdevices. The reflecting plate 2 reflects a light generated by the lightgenerating units 4 to the light guiding plate 3. The light guiding plate3 guides the light to the LCD panel (not shown).

The light generating unit 4 is installed on one or two sides of thesupport frame 1, and the support elements 31 are formed on the two endsof the side(s). Two sides of the light guiding plate 3 have supportstands 32 that have support elements 31 thereon. Coupling elements 41are installed on the two ends of light generating unit 4 respectively,and support elements 31 on the support stands 32 and the couplingelements 41 engage. Moreover, the coupling elements 41 respectively havea conductive wire 44 to electrically connect with power supply. The twosides of the reflecting plate 2 extend an estimated length, and theextend portions are rolled upward, and an L-shaped upper cover coversthe light generating unit 4. The L-shaped upper cover can be fixed byadhesive (e.g., twin adhesive) or tongue-and-groove joint. As shown inFIG. 6, engaging elements 61 and 33 engage to fix the L-shaped uppercover for arriving at the function of lamp reflector.

In the embodiment, the engaging elements can be a protruding and ahollow to provide inter-engaged.

In such case, the electromagnetic interference (EMI) can be eliminatedby coating, covering, or pasting with a metallic material (not shown) onthe surface(s) of the coupling elements 41 or any one surface ofreflecting plate 2. Therefore, the present invention can eliminate EMIproblems. The metallic material can be any metal capable of isolatingEMI, such as Cu, Ni, Al, or the combination thereof. Moreover, thequantity of the light generating unit can be one or many, depending onthe desired purpose. In general, there are two light generating unitsrespectively on the two sides of the back light module.

FIG. 6 illustrates a partial schematic diagram of the engaging actionfor the coupling elements 41 of the light generating unit 4 and thesupport element 31 of the support stand 32 in FIG. 3.

In the second embodiment mentioned above, the light generating unit isinstalled in light guiding plate by forming an indentation in one sideof the light guiding plate to contain the light generating unit.Furthermore, two ends of the indentation have the engaging elementcorresponding to the coupling element (e.g., silica gel) to fix thelight generating unit. In practice, one or many protruding may be formedin the indentation to fix the light generating unit more stably. Thefunction of the protruding is similar to the function of O-ring that isused in the lamp of lamp module in the conventional arts. However, theprotruding is unnecessary if the light generating unit comprises theO-ring thereon.

In the three embodiments mentioned above, the bending status of the twosides of the reflecting plate is not only right-angled, as shown infigures, but also is curviform. The light generating units can be placedin the bent two side of the reflecting plate or in the indentations ofthe light guiding plate.

In the present invention, the support frame having support elements canbe manufactured by integrated method like plastic mold injection, so itis very simple for manufacturing. In order to make the reflecting plateeasily bend, the stitching line can be formed on the reflecting plate.

Moreover, in accordance with the back light module of the presentinvention, the reflecting plate generally is made of PET (Poly(ethyleneterephthalate)), and a light reflecting layer (e.g., TiO₂, Ag) is coatedthereon. It is preferred that the light reflecting layer is TiO₂ foravoiding the phenomenon of color density shift resulted from absorbingpartial visible light.

The back module of LCD device according to the present invention, theoptical films is the conventional optical films for LCD device,comprising a diffusing film, a light condensing film, a lightenhancement film, a prism film, and so on.

In accordance with the embodiments of the present invention mentionedabove, the problems of light leakage, dark stripe, wrinkling, and EMInow can all be eliminated.

1. A back light module of LCD device, comprising: a support frame havingsupport elements thereon; at least one light generating unit having twocoupling elements to engage with said support elements respectivelyinstalled on two ends of at least one said light generating unit; alight reflecting plate installed on said support frame for reflecting alight generated by at least one said light generating unit upwards, andtwo ends of said reflecting plate bent upward; and a light guiding plateinstalled on said reflecting plate for guiding light; wherein a metallicmaterial for isolating electromagnetic interference is installed on asurface of said reflecting plate, a surface of said coupling elements,or the combination thereof.
 2. The back light module according to claim1, wherein material of said coupling elements is silica gel.
 3. The backlight module according to claim 1, wherein said metallic material forisolating electromagnetic interference is Cu, Ni, Al, or the combinationthereof.
 4. The back light module according to claim 1, wherein saidreflecting plate is divided into two portions for covering said lightgenerating unit.
 5. The back light module according to claim 4, whereinsaid reflecting plate is composed of an upper cover and a bottomreflecting plate.
 6. The back light module according to claim 5, whereinsaid upper cover is L-shaped.
 7. The back light module according toclaim 5, wherein said bottom reflecting plate has two ends bent upward.8. A back light module of LCD device, comprising: a support frame; alight reflecting plate installed on said support frame, and two ends ofsaid reflecting plate bent upward; a light guiding plate installed onsaid reflecting plate, two side of said light guiding plate respectivelyhaving an indentation, and support elements are formed in saidindentations; at least one light generating unit installed incorresponding indentation, said light reflecting plate reflecting lightgenerated by at least one said light generating unit upwards, said lightguiding plate for guiding light, and at least one said light generatingunit having two coupling elements to engage with said support elementsrespectively installed on two ends thereof; wherein a metallic materialfor isolating electromagnetic interference is installed on a surface ofsaid reflecting plate, a surface of said coupling elements, or thecombination thereof.
 9. The back light module of LCD penal according toclaim 8, wherein material of said coupling elements are silica gel. 10.The back light module according to claim 8, wherein said metallicmaterial is Cu, Ni, Al, or the combination thereof.
 11. The back lightmodule according to claim 8, wherein said reflecting plate is composedof an upper cover and a bottom reflecting plate.
 12. The back lightmodule according to claim 11, wherein said bottom reflecting plate hastwo ends bent upward.
 13. The back light module according to claim 11,wherein said upper cover is L-shaped.
 14. A back light module of LCDdevice, comprising: a support frame; at least one light generating unithaving two coupling elements respectively installed on two ends of atleast one said light generating unit; a light reflecting plate installedbetween at least one said light generating unit and said support framefor reflecting a light generated by at least one said light generatingunit upwards, and two ends of said reflecting plate bent upward; and alight guiding plate installed on said reflecting plate for guidinglight, and said light guiding plate having support elements that engagewith said coupling elements to fix at least one said light generatingunit on said support frame; wherein a metallic material for isolatingelectromagnetic interference is installed on a surface of saidreflecting plate, a surface of said coupling elements, or thecombination thereof.
 15. The back light module according to claim 14,wherein material of said coupling elements are silica gel.
 16. The backlight module according to claim 14, wherein said reflecting plate iscomposed of an upper cover and a bottom reflecting plate.
 17. The backlight module according to claim 16, wherein said bottom reflecting platehas two ends bent upward.
 18. The back light module according to claim16, wherein said upper cover is L-shaped.